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101.
Subhabrata Maiti Krishnendu Das Sounak Dutta Prof. Prasanta Kumar Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(47):15021-15030
This work demonstrates a remarkable enhancement in the peroxidase activity of mitochondrial membrane protein cytochrome c (cyt c) by perturbing its tertiary structure in the presence of surface‐functionalised gold nanoparticles (GNPs) within cetyltrimethylammonium bromide (CTAB) reverse micelles. The loss in the tertiary structure of cyt c exposes its heme moiety (which is buried inside in the native globular form), which provides greater substrate (pyrogallol and H2O2) accessibility to the reactive heme residue. The surfactant shell of the CTAB reverse micelle in the presence of co‐surfactant (n‐hexanol) exerted higher crowding effects on the interfacially bound cyt c than similar anionic systems. The congested interface led to protein unfolding, which resulted in a 56‐fold higher peroxidase activity of cyt c than that in water. Further perturbation in the protein’s structure was achieved by doping amphiphile‐capped GNPs with varying hydrophobicities in the water pool of the reverse micelles. The hydrophobic moiety on the surface of the GNPs was directed towards the interfacial region, which induced major steric strain at the interface. Consequently, interaction of the protein with the hydrophobic domain of the amphiphile further disrupted its tertiary structure, which led to better opening up of the heme residue and, thereby, superior activity of the cyt c. The cyt c activity in the reverse micelles proportionately enhanced with an increase in the hydrophobicity of the GNP‐capping amphiphiles. A rigid cholesterol moiety as the hydrophobic end group of the GNP strikingly improved the cyt c activity by up to 200‐fold relative to that found in aqueous buffer. Fluorescence studies with both a tryptophan residue (Trp59) of the native protein and the sodium salt of fluorescein delineated the crucial role of the hydrophobicity of the GNP‐capping amphiphiles in improving the peroxidase activity of cyt c by unfolding its tertiary structure within the reverse micelles. 相似文献
102.
Debapriya Chakraborty Nilanjana Bose Sukanya Sasmal Swagata Dasgupta Tapas K. Maiti Suman Chakraborty Sunando DasGupta 《Analytica chimica acta》2012
Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates. 相似文献
103.
Mohammad Shahid Syed S. Razi Priyanka Srivastava Rashid Ali Biswajit Maiti Arvind Misra 《Tetrahedron》2012,68(44):9076-9084
A new simple organic scaffold based on acenaphthene 4 was designed and synthesized. The chromogenic and fluorogenic properties of 4 toward different metal ions and anions were investigated in H2O/MeCN (8:2, v/v) solution. The probe 4 in the presence of Cu2+ exhibited strong static excimer emission at 507 nm along with a decrease in monomer emission at ~400 nm ratiometrically, attributed to a complexation through aldimine and amide groups of 4. Additionally, 4 upon interaction with different anions illustrated significant fluorescence enhancement with cyanide. However, interaction of complex, 4-Cu2+ with CN? revealed fluorescence quenching attributed to formation of stable [Cu(CN)x]1?x species in the medium. A naked-eye sensitive fluorescent green color of solution was changed to blue. The mechanism of interaction between 4 and Cu2+ and sensing of cyanide through Cu2+ displacement approach was confirmed by the change in optical behaviors and 1H NMR and ESI-MS spectral data analysis. 相似文献
104.
S Mogurampelly S Panigrahi D Bhattacharyya AK Sood PK Maiti 《The Journal of chemical physics》2012,137(5):054903
Using all atom molecular dynamics simulations, we report spontaneous unzipping and strong binding of small interfering RNA (siRNA) on graphene. Our dispersion corrected density functional theory based calculations suggest that nucleosides of RNA have stronger attractive interactions with graphene as compared to DNA residues. These stronger interactions force the double stranded siRNA to spontaneously unzip and bind to the graphene surface. Unzipping always nucleates at one end of the siRNA and propagates to the other end after few base-pairs get unzipped. While both the ends get unzipped, the middle part remains in double stranded form because of torsional constraint. Unzipping probability distributions fitted to single exponential function give unzipping time (τ) of the order of few nanoseconds which decrease exponentially with temperature. From the temperature variation of unzipping time we estimate the energy barrier to unzipping. 相似文献
105.
Avijit Banerji Kaustabh Kumar Maiti Sunanda Haldar Chaitali Mukhopadhyay Julie Banerji Thierry Prangé Alain Neuman 《Monatshefte für Chemie / Chemical Monthly》2000,131(8):901-911
Summary. Studies on cycloadditions of C,N-diarylnitrones to cinnamic acid amides were carried out. The diastereoisomeric (I, II) and (in some cases) regioisomeric (III) cycloadducts obtained were characterized by spectroscopic and X-ray data. Conformational studies were carried out by molecular
modelling.
Received February 8, 2000. Accepted February 18, 2000 相似文献
106.
Pralay Maiti Ganga Radhakrishnan Palanisamy Aruna Goutam Ghosh 《Macromolecular Symposia》2006,241(1):51-59
Novel polyurethane gels have been reported in common solvent like dimethyl formamide (DMF). Polyurethanes have been synthesized from diisocyanates, diols and rigid chain extenders. We have illustrated the influence of chemical structure of the chain extenders on gelation rate, thermal property and morphology of the gels in DMF. Gelation rate increases significantly with the rigidity of the chain extender. Introduction of more rigid chain extender molecules in polyurethane prepolymer enhanced the thermal stability of the pure polymer. On the contrary, the solvent retention power of the gels gradually decreases with increasing rigidity of chain extender presumably because of the poor dispersion/greater aggregation of the hard segments in the soft segment matrix. Morphology and formation of gelation have been discussed. 相似文献
107.
Dipsikha Bhattacharya Sumanta K. Sahu Indranil Banerjee Manasmita Das Debashish Mishra Tapas K. Maiti Panchanan Pramanik 《Journal of nanoparticle research》2011,13(9):4173-4188
In this article, we report the design and synthesis of a series of well-dispersed superparamagnetic iron oxide nanoparticles
(SPIONs) using chitosan as a surface modifying agent to develop a potential T
2 contrast probe for magnetic resonance imaging (MRI). The amine, carboxyl, hydroxyl, and thiol functionalities were introduced
on chitosan-coated magnetic probe via simple reactions with small reactive organic molecules to afford a series of biofunctionalized
nanoparticles. Physico-chemical characterizations of these functionalized nanoparticles were performed by TEM, XRD, DLS, FTIR,
and VSM. The colloidal stability of these functionalized iron oxide nanoparticles was investigated in presence of phosphate
buffer saline, high salt concentrations and different cell media for 1 week. MRI analysis of human cervical carcinoma (HeLa)
cell lines treated with nanoparticles elucidated that the amine-functionalized nanoparticles exhibited higher amount of signal
darkening and lower T
2 relaxation in comparison to the others. The cellular internalization efficacy of these functionalized SPIONs was also investigated
with HeLa cancer cell line by magnetically activated cell sorting (MACS) and fluorescence microscopy and results established
selectively higher internalization efficacy of amine-functionalized nanoparticles to cancer cells. These positive attributes
demonstrated that these nanoconjugates can be used as a promising platform for further in vitro and in vivo biological evaluations. 相似文献
108.
109.
The 11S→23S excitation of Li+ has been studied in the Coulomb-Born-Oppenheimer approximation. The differential and the total cross sections are given at double the threshold energy. 相似文献
110.
Kumar H Mukherjee B Lin ST Dasgupta C Sood AK Maiti PK 《The Journal of chemical physics》2011,134(12):124105
Experiments and computer simulations demonstrate that water spontaneously fills the hydrophobic cavity of a carbon nanotube. To gain a quantitative thermodynamic understanding of this phenomenon, we use the recently developed two phase thermodynamics method to compute translational and rotational entropies of confined water molecules inside single-walled carbon nanotubes and show that the increase in energy of a water molecule inside the nanotube is compensated by the gain in its rotational entropy. The confined water is in equilibrium with the bulk water and the Helmholtz free energy per water molecule of confined water is the same as that in the bulk within the accuracy of the simulation results. A comparison of translational and rotational spectra of water molecules confined in carbon nanotubes with that of bulk water shows significant shifts in the positions of the spectral peaks that are directly related to the tube radius. 相似文献